Primary sources: also called contemporary sources: material from the time period of an event or a historical period, created by the people or institutions involved. Letters, diaries, government reports, church records, civil records (birth/death/marriage), newspaper/magazine articles/books, fliers, posters, political cartoons, etc. can all be considered primary sources. They can be published or unpublished, and found in libraries or archives. Secondary sources are books or articles written from these materials at a later date.
Examples: An article in the Baltimore Sun, about the Great Baltimore Fire (1904), published in 1904; H.L. Mencken's autobiography, describing what he was doing during the Fire (published many years later); and letters from ordinary Baltimore people who lived through the Fire (unpublished, in a collection) are all primary sources. A book about the Fire, using these, would be a secondary source.
Archives/archival collections: Archives are where records and publications from governments, institutions, or organizations are stored. The UMBC archives are kept in the Special Collections Department and include records from the UMBC administration, course catalogs, copies of the Retriever, and other material produced by the University. Archival collections is a broader term for unpublished material kept and arranged by archivists.
Finding Aid: A detailed description of a collection including a scope and content note and a list of what each box in the collection contains. Finding aids can but do not normally have links to the full text of the documents they describe.
Published/Unpublished: Primary sources can be published material: newspapers, books, or reports written at the time or collections of letters, oral histories, or diaries collected and arranged without editing the content are all legitimate. Published sources like these can be found in library catalogs and databases, and there will be multiple copies available. Unpublished sources are rarely available outside of archives and usually must be visited where they are held. Finding aids to unpublished collections can be found in catalogs and databases, but the full text will rarely be included.